1. Field
Aspects of the present disclosure relate to electrode catalysts that are used in a fuel cell, membrane electrode assemblies and fuel cells including the electrode catalysts, and methods of preparing the electrode catalysts.
2. Description of the Related Art
A fuel cell contains an electrolyte disposed between two electrodes, which are generally formed of porous metal or carbon. Such a fuel cell is also referred to as a single cell. Hydrogen gas or another fuel is supplied to an anode from outside the fuel cell, reaches a reaction region through pores of the electrode, and turns into dissociated hydrogen atoms by being adsorbed to a catalyst in the electrode. The active hydrogen atoms turn into protons, and two electrons are transmitted to the electrode. The electrons are transferred to a cathode, which is on the opposite side of the anode, through an external circuit. Accordingly, a current is generated by the fuel cell. Water is generated at the cathode due to oxygen supplied from outside the fuel cell, the protons transported through the electrolyte, and the electrons transmitted through the external circuit reacting with each other.
An anode in a polymer electrolyte membrane fuel cell (PEMFC) may include a platinum catalyst to accelerate a reaction that generates protons by oxidizing hydrogen gas. For example, a supported catalyst may include platinum and molybdenum carbide or tungsten carbide covering a part or the whole area of the surface of a support. However, platinum is expensive and in limited supply, and thus, the use of platinum hinders widespread commercialization of such fuel cells. In order to reduce the amount of a platinum catalyst used, carbonaceous materials that have a large specific surface area and are conductive may be used as a support, and the specific surface area of a platinum catalyst is increased by uniformly depositing minute platinum particles on the support. However, the weight of a platinum catalyst component is generally 40 to 80 wt % based on the entire weight of a supported catalyst, and thus, such fuel cells are expensive.